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I've not been able to find a single reference to methane production from sanitary septic systems. Has anyone done any research in this area? I assume that it must not be worthwhile but I know very little on the topic. Just curious and this seems like a good place to ask.thanks chris

Hi ChrisOn a Russian language forum member AleseyA once put up pictures and text to a current day Vietnamese govenment sponsored rural inititive to devepope and build 100's of thousands of individual below ground beehive shaped sewage digesters. Program was to clean up and preserve ground water contamination in their wet environment and supply domestic individual cooking gas.Try google searching from this direction.RegardsSteve Unruh

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Thanks for the tip Steve. Did find some interesting info, but not a lot of detail. Ran across a number of articles about feedlot sized systems, but really nothing much smaller. I've been thinking about all the bio waste generated by a typical residence (not only sewage but food, grass clippings, leaves, etc) and wondered about the viability of a small digester system. From what I've read, the process is simple, but the mechanics of something useful appear to get fairly complex (read: expensive) so I suspect that's why there's not been much work done at a small scale.cheers,chris

I've found some useful engineering texts and articles on the topic of waste water based production. To distill the math down, the short answer is that you can get slightly less than 1 cubic foot of methane per day per person. A candle would be more useful. I'm trying to work out how much waste plant biomass might be necessary to get a reasonable quantity of fuel gas now. Appears that different "bugs" are involved, but gas production can be much higher since much of the energy has already been removed from waste water (biologically speaking). Between tree leaves and grass clippings, I could supply quite a bit of plant material....still have much to learn, but an interesting topic!

This sure is possible. It's my daily job, but then with 50% cow manure and 50% dairy/food/industrial organic waste.

Thing is that with a little sewage from your household, you wont get much biogas. With other organic waste you can put up your gas production. Simple trick to predict the succes is look at how fast it normally decomposes. The faster it composes, the faster it will digest. Oak leafs for example, don't go away very fast. Wood takes ages. This is not suitable for digestion. Drying them and burning would work better.

But leftovers, like patatos, vegetables, meat: Grind it up, feed the digester and it will have a feast.

Then also problems like cleaning detergents, medicine and too much salts can destroy your biology. If its not good for you, the digester will not like it too.

Antoher problem with sewage is the dry matter. You flush 100gram, if your a real man, 200gram of shit away with 6-9 liters of water. The pile contains about 10-20% dry matter, and I'm guessing that dry matter contains about 80% organic matter. This would work, but with the 6-9 liters of water you also flush out your bacteria from the digester. Separating would give better results.

The easiest way to use the biogas is in your stove. Buffer it in a old inner truck tyre, stones on top for pressure. Make sure all water can drain out before use. Condensate has to be run down to the digester. Untreated biogas is corrosive. Your stove will not care, but a motor, central heating will corrode due to H2S, NH3 and condensate.

If you have question ask, I'll have the same plans for a while, but no time.

from here you will find some knowledge collections in case you have not already found them.

and yes, the usual problem for the diyer is to get enough gas for anything more than a stove. one needs a highly concentrated production situation, like a feed lot or dairy, to get a feedstock volume to do much. the payback is the tech is much more simple than thermal conversion of dry material.

all these alt energy solutions are very context specific. none are general case silver bullets.